Rapid Normal Stress Oscillations Cause Weakening and Anelastic Dilation in Gouge-Bearing Faults

Jianye Chen*, Andre R. Niemeijer, Christopher J. Spiers

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Fault normal stress (σn) changes dynamically during earthquakes. However, the impact of these changes on fault strength is poorly understood. We explore the effects of rapidly varying σn by conducting rotary-shear experiments on simulated fault gouges at 1 μm/s, under well-drained, hydrothermal conditions. Our results show both elastic and anelastic (time-dependent but recoverable) changes in gouge layer thickness in response to step changes and sinusoidal oscillations in σn. In particular, we observe dilation associated with marked weakening during ongoing σn-oscillations at frequencies >0.1 Hz. Moreover, recovery of shear stress after such oscillations is accompanied by transient (anelastic) compaction. We propose a microphysically based friction model that explains most of the observations made, including the effects of temperature and step versus sinusoidal perturbation modes. Our results highlight that σn-oscillations above a specific frequency threshold, controlled by the loading regime and frictional properties of the fault, may enhance seismic hazards.

Original languageEnglish
Article numbere2024GL109755
JournalGeophysical Research Letters
Volume51
Issue number15
DOIs
Publication statusPublished - 16 Aug 2024

Bibliographical note

Publisher Copyright:
© 2024. The Author(s).

Funding

This study is co-supported by the National Science Foundation (4217040794) and the DeepNL project (Science4Steer).

FundersFunder number
National Science Foundation4217040794
DeepNL project (Science4Steer)

    Keywords

    • fault dilation
    • induced seismicity
    • normal stress modulations
    • stress perturbation
    • vibration-induced fault weakening

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